;;; Hey, emacs, this file is -*- Mode: tdl; -*- ... got that?

;;;
;;; the type hierachy, introducing sub-types and appropriate features
;;;


feat-struc := *top*.

expression := feat-struc & 
[ HEAD pos,
  VAL valence ].

valence := feat-struc &
[ SPR *list*,
  COMPS *list* ].

pos := feat-struc &
[ MOD *list* ].

pos-agr := pos &
[ AGR pernum,
  MOD < > ].

pernum := feat-struc.
3sing := pernum.
non-3sing := pernum.

noun := pos-agr.

verb := pos-agr.

det := pos-agr.

pre-mod := pos.

post-mod := pos.

adj := pre-mod &
[ MOD < [ HEAD noun ] > ].

adv := post-mod & pre-mod &
[ MOD < [ HEAD verb ] > ].

prep := post-mod &
[ MOD < expression >,
  FORM *string* ].

phrase := expression &
[ ARGS *list* ].

head-initial := phrase & 
[ HEAD #head,
  ARGS [ FIRST [ HEAD #head ] ] ].

head-final := phrase & 
[ HEAD #head,
  ARGS < expression, [ HEAD #head ] > ].

word := expression &
[ ORTH *string* ].

root := phrase &
[ HEAD verb,
  VAL [ SPR < >,
        COMPS < > ] ].

root-head-initial := root & head-initial.

root-head-final := root & head-final.

;;;
;;; a few `non-linguistic' types: the top type for all strings (i.e. type names
;;; enclosed in double quotes; no need to declare strings individually) and the
;;; hierarchy of list types (using a FIRST -- REST encoding for list elements
;;; and list tails, respectively).
;;;

*string* := *top*.

*list* := *top*.

*ne-list* := *list* &
 [ FIRST *top*,
   REST *list* ].

*null* := *list*.